China “strongly condemns” the incident and calls on Myanmar to carry out a thorough investigation, report the findings to China, punish the guilty and take steps to ensure similar events do not occur, the ministry said in a statement.

Beijing has disavowed any links with the ethnic Chinese rebels in Myanmar, saying it respects Myanmar’s sovereignty. Myanmar officials have said former Chinese soldiers have trained the rebels, an allegation the insurgents have denied.

A Myanmar official denied bombing China and said rebels may have caused the explosion. “It’s possible that those fighting with us purposely created these attacks with the intent of causing mis- understanding between China and us,” the official said.

Clashes between Myanmar’s military and rebel fighters known as the Myanmar National Democratic Alliance Army (MNDAA) have intensified since last month.

Senior Myanmar officials blame the renewed fighting on a renegade rebel faction led by Phone Kya Shin, which attempted to seize Laukkai, the capital of the self-administered Kokang region. Myanmar has said Chinese mercenaries were fighting with the rebels, and it has urged China to co-operate to prevent “terrorist attacks” being launched from Chinese territory.

The creation of the Kokang Special Region dates back to the collapse of the Burmese Communist Party in 1989.

In return for peace, the Burmese government gave splinter groups like the Wa and the Kokang pieces of land and a large degree of autonomy.

For leaders like Kokang’s Phone this was the green light to expand already prodigious arms and drug-trafficking networks. US officials have long suspected Phone, of playing a major role in drug trafficking, initially in opium and more recently in methamphetamines.

The Kokang are recognised as an ethnic group in Myanmar but in language and culture they are very much Chinese. In this special region you can use a Chinese phone network and spend Chinese money.

The guerrillas used to be part of the now-defunct Burmese Communist Party, which had been backed by China until it signed a ceasefire with the then-military government in Myanmar in 1989. The MNDAA truce with the government lasted until 2009, when government troops took over their region in a conflict that pushed tens of thousands of refugees into China.

China recently warned Myanmar that the escalating conflict in Kokang could destabilise the border area. Some 30,000 refugees have fled the conflict for China.

Myanmar is fighting ethnic Han Chinese rebels in the remote region, in its north-western state of Shan.